The invention is relative to a series [line] for gear pumps with differing capacities and to a method of manufacturing the individual gear pumps of the series.
Hydraulic pumps in the form of gear pumps in which two gears meshing with one another, running with close tolerance in a housing and used as displacing elements are known in a plurality of designs. As regards the type of displacing elements, two types are distinguished:
a) Gear pumps with external gearing [toothing],
b) Gear pumps with internal gearing.
See in this connection Dubbel: Taschenbuch fxc3xcr den Maschinenbau [German-Pocketbook for Machine Construction], 18th edition, H4 to H5. Pumps with internal gearing are known, e.g., from Voith publication G 1210 8.80 1000. The main characteristics of a hydraulic pump are the geometric displacement volume and the nominal pressure. Due to the very varied areas of application and the requirements of use resulting therefrom, hydraulic pumps for differing output [delivery] volumes are offered. The work takes place as a rule in series in that the individual pumps of a series have the same construction but differ significantly from each other in their characteristics. An enlargement of the construction size is associated with a corresponding increase in the output volume. This can be gathered, e.g., from Voith publication 3.83, pp. 4 to 5 in the example of a pump with internal gearing. The enlargement of the possible output flow takes place at rather large intervals in groups. The essential distinguishing feature between the groups resides in either the differing radial or axial dimension of the displacing elements. Within the groups an elevation of the possible output volume takes place in smaller steps by enlarging the gearing width, that is, the extension of the gearing in axial direction. This has the result that the individual pumps in drive [train] lines are not freely exchangeable as a rule if the requirements of use are changed since the latter differ sharply as regards the required construction space and similarities between the individual types can hardly be determined.
The invention therefore has the basic problem of creating a series for gear pumps for differing output volumes that are therefore suitable for different requirements of use in which series the individual pumps have as many constructive features in common as possible and differ solely by slight inner modifications. The pumps themselves are to be kept as small as possible as regards the required construction space and there should be the possibility of replacement with a pump with a greater or lesser output volume in hydrostatic systems without the entire drive chain having to be replaced.
The solution of the invention is characterized by the features of claim 1. Advantageous embodiments are described in the subclaims.
A series of gear pumps for differing output volumes comprises at least two pumps. Each pump comprises at least two gears meshing with one another as displacer or displacing elements. The invention provides that each pump in the series has the following construction features that are essentially identical as regards the dimension:
a) Axial [shaftxe2x80x94German xe2x80x9cAchsexe2x80x9d=axis, axle and shaft] interval between the axes [shafts] of the two gears meshing with one another,
b) Gearing width, that is, extension of the gearing in axial direction.
That is, the pumps of the series all have the same axial interval and the same gearing width.
However, the indication xe2x80x9cessentially identicalxe2x80x9d should include customary finishing tolerances.
The differing output volumes are adjusted in accordance with the invention in pumps of a series with the same axial interval between the individual displacing elements and a constant gearing width over the cog height. It is sufficient thereby if at least one of the two gears meshing with one another is changed as regards its tip [addendum] circle diameter; however, it is preferable if both gears are changed as regards their tip circle diameter.
The inventor realized that relatively high output volumes can be achieved when using so-called high gearings since the sensitivity oft he output volume over the tip circle diameter or the tip circle radius is significantly higher than in the case of normal gearings. Even slight changes in the tip circle are sufficient to achieve a corresponding increase of the output volume. The volumetric increase in radial direction of the individual pump relative to the axes of the displacing elements or of the axes of symmetry of the displacing elements is relatively slight. This statement also applies in an analogous manner to a diminution of the tip circle diameter or tip circle radius of an individual displacing element. The axial construction length remains constant for all gear pumps of the series. A change takes place only in radial direction during which only a lesser increase in volume for the entire gear pump construction unit is realized on account of the high sensitivity of output volume over the tip circle radius. The uniform axial construction length of the gear pump construction unit makes it possible to replace the gear pump arranged in a drive chain in accordance with the requirements of use on the volume to be delivered with another gear pump of this series that is designed for greater or lesser output volumes without the entire drive chain having to be replaced or readapted to the hydraulic pump to be used.
In an especially preferred embodiment of the gear pump series a constant transverse pitch p is assigned to the particular displacing elements, that is, gears of the individual pumps in the series, in the case of an axial interval that can be predefined and is constant for all pumps in the series, that is, the modulus as dimensional factor of the gearing is also constant for all pumps so that there is the possibility of developing the displacing elements for the individual gear pumps with differing output volumes from a pump arrangement with a unified basic displacing element as described, e.g., in claim 8, in which the basic gearing is designed for a maximum output volume of at least one of the two displacing elements as a high gearing and for a minimum output volume the gearing or the individual cog [tooth] elements are reduced in size [by removing metal] or milled down correspondingly to a smaller tip circle diameter. This procedure makes it possible to create a series for gear pumps with different output volumes in which the individual gear pumps are designed to be especially compact and very standardized as regards the individual elements. The high degree of standardization results in a diminution of the manufacturing cost, which for its part is reflected in the [total] cost.
The design of the basic construction unit for the maximum output volume as regards the individual gears meshing with each other takes place in accordance with the fundamentals of the geometry of gear pairs. This applies to the general instance that influence is exerted only on the cog height, regardless of the form, and to the especially advantageous embodiment in which, starting from a displacing element designed for maximum output volume, lesser output volumes can be realized by shortening the cog height, that is, removing material.
The solution of the invention can be used in gear pumps with
a) external gearing,
b) internal gearing.
It is immaterial thereby whether the gear pumps are single-flow or multiflow gear pumps.
In gear pumps with externally cogged displacing elements both displacing elements are preferably designed and constructed to be similar in their size and gearing geometry whereas in the case of dual-flow or multiflow gear pumps displacing elements with differing designs and dimensions are used.